The present invention generally relates to a non-tower process for producing a particulate detergent composition. More particularly, the invention is directed to a continuous process during which detergent agglomerates are produced by feeding a surfactant and coating materials into a series of mixers. The process produces a free flowing, detergent composition whose density can be adjusted for wide range of consumer needs, and which can be commercially sold.
Recently, there has been considerable interest within the detergent industry for laundry detergents which are xe2x80x9ccompactxe2x80x9d and therefore, have low dosage volumes. To facilitate production of these so-called low dosage detergents, many attempts have been made to produce high bulk density detergents, for example with a density of 600 g/l or higher. The low dosage detergents are currently in high demand as they conserve resources and can be sold in small packages which are more convenient for consumers. However, the extent to which modern detergent products need to be xe2x80x9ccompactxe2x80x9d in nature remains unsettled. In fact, many consumers, especially in developing countries, continue to prefer a higher dosage levels in their respective laundering operations.
Generally, there are two primary types of processes by which detergent granules or powders can be prepared. The first type of process involves spray-drying an aqueous detergent slurry in a spray-drying tower to produce highly porous detergent granules (e.g., tower process for low density detergent compositions). In the second type of process, the various detergent components are dry mixed after which they are agglomerated with a binder such as a nonionic or anionic surfactant, to produce high density detergent compositions (e.g., agglomeration process for high density detergent compositions). In the above two processes, the important factors which govern the density of the resulting detergent granules are the shape, porosity and particle size distribution of said granules, the density of the various starting materials, the shape of the various starting materials, and their respective chemical composition.
There have been many attempts in the art for providing processes which increase the density of detergent granules or powders. Particular attention has been given to densification of spray-dried granules by post tower treatment. For example, one attempt involves a batch process in which spray-dried or granulated detergent powders containing sodium tripolyphosphate and sodium sulfate are densified and spheronized in a Marumerizer(copyright). This apparatus comprises a substantially horizontal, roughened, rotatable table positioned within and at the base of a substantially vertical, smooth walled cylinder. This process, however, is essentially a batch process and is therefore less suitable for the large scale production of detergent powders. More recently, other attempts have been made to provide continuous processes for increasing the density of xe2x80x9cpost-towerxe2x80x9d or spray dried detergent granules. Typically, such processes require a first apparatus which pulverizes or grinds the granules and a second apparatus which increases the density of the pulverized granules by agglomeration. While these processes achieve the desired increase in density by treating or densifying xe2x80x9cpost towerxe2x80x9d or spray dried granules, they are limited in their ability to go higher in surfactant active level without subsequent coating step. In addition, treating or densifying by xe2x80x9cpost towerxe2x80x9d is not favourable in terms of economics (high capital cost) and complexity of operation. Moreover, all of the aforementioned processes are directed primarily for densifying or otherwise processing spray dried granules. Currently, the relative amounts and types of materials subjected to spray drying processes in the production of detergent granules has been limited. For example, it has been difficult to attain high levels of surfactant in the resulting detergent composition, a feature which facilitates production of detergents in a more efficient manner. Thus, it would be desirable to have a process by which detergent compositions can be produced without having the limitations imposed by conventional spray drying techniques.
To that end, the art is also replete with disclosures of processes which entail agglomerating detergent compositions. For example, attempts have been made to agglomerate detergent builders by mixing zeolite and/or layered silicates in a mixer to form free flowing agglomerates. While such attempts suggest that their process can be used to produce detergent agglomerates, they do not provide a mechanism by which starting detergent materials in the form of pastes, liquids and dry materials can be effectively agglomerated into crisp, free flowing detergent agglomerates.
Accordingly, there remains a need in the art to have an agglomeration (non-tower) process for continuously producing a detergent composition having high density delivered directly from starting detergent ingredients, and preferably the density can be achieved by adjusting the process condition. Also, there remains a need for such a process which is more efficient, flexible and economical to facilitate large-scale production of detergents (1) for flexibility in the ultimate density of the final composition, and (2) for flexibility in terms of incorporating several different kinds of detergent ingredients, especially detergent ingredients in the form of liquid, into the process.
The following references are directed to densifying spray-dried granules: Appel et al, U.S. Pat. No. 5,133,924 (Lever); Bortolotti et al, U.S. Pat. No. 5,160,657 (Lever); Johnson et al, British patent No. 1,517,713 (Unilever); and Curtis, European Patent Application 451,894.
The following references are directed to producing detergents by agglomeration: Beujean et al, Laid-open No. WO93/23,523 (Henkel), Lutz et al, U.S. Pat. No. 4,992,079 (FMC Corporation); Porasik et al, U.S. Pat. No. 4,427,417 (Korex); Beerse et al, U.S. Pat. No. 5,108,646 (Procter and Gamble); Capeci et al, U.S. Pat. No. 5,366,652 (Procter and Gamble); Hollingsworth et al, European Patent Application 351,937 (Unilever); Swatling et al, U.S. Pat. No. 5,205,958; Dhalewadikar et al, Laid Open No.WO96/04359 (Unilever).
For example, the Laid-open No.WO93/23,523 (Henkel) describes the process comprising pre-agglomeration by a low speed mixer and further agglomeration step by high speed mixer for obtaining high density detergent composition with less than 25 wt % of the granules having a diameter over 2 mm. The U.S. Pat. No. 4,427,417 (Korex) describes continuous process for agglomeration which reduces caking and oversized agglomerates.
None of the existing art provides all of the advantages and benefits of the present invention.
The present invention meets the aforementioned needs in the art by providing a process which produces a high density granular detergent composition. The present invention also meets the aforementioned needs in the art by providing a process which produces a granular detergent composition for flexibility in the ultimate density of the final composition from agglomeration (e.g., non-tower) process. The process does not use the conventional spray drying towers currently which is limited in producing high surfactant loading compositions. In addition, the process of the present invention is more efficient, economical and flexible with regard to the variety of detergent compositions which can be produced in the process. Moreover, the process is more amenable to environmental concerns in that it does not use spray drying towers which typically emit particulates and volatile organic compounds into the atmosphere.
As used herein, the term xe2x80x9cagglomeratesxe2x80x9d refers to particles formed by agglomerating raw materials with binder such as surfactants and or inorganic solutions/organic solvents and polymer solutions. As used herein, the term xe2x80x9cgranulatingxe2x80x9d refers to fluidizing agglomerates thoroughly for producing free flowing, round shape granulated-agglomerates. As used herein, the term xe2x80x9cmean residence timexe2x80x9d refers to following definition:
mean residence time (hr)=mass (kg)/flow throughput (kg/hr)
All percentages used herein are expressed as xe2x80x9cpercent-by-weightxe2x80x9d unless indicated otherwise. All ratios are weight ratios unless indicated otherwise. As used herein, xe2x80x9ccomprisingxe2x80x9d means that other steps and other ingredients which do not affect the result can be added. This term encompasses the terms xe2x80x9cconsisting ofxe2x80x9d and xe2x80x9cconsisting essentially ofxe2x80x9d.
In accordance with one aspect of the invention, a process for preparing a granular detergent composition having a density at least about 600 g/l is provided.
The process comprises the steps of:
(a) dispersing a surfactant, and coating the surfactant with fine powder having a diameter from 0.1 to 500 microns, while wetting the surfactant coated with the fine powder with finely atomized liquid, in a mixer wherein conditions of the mixer include (i) from about 0.2 to about 5 seconds of mean residence time, (ii) from about 10 to about 30 m/s of tip speed, and (iii) from about 0.15 to about 5 kj/kg of energy condition, wherein agglomerates are formed; and
(b) thoroughly mixing the agglomerates in a mixer wherein conditions of the mixer include (i) from about 0.5 to about 15 minutes of mean residence time and (ii) from about 0.15 to about 7 kj/kg of energy condition.
Also provided is a process for preparing a granular detergent composition having a density at least about 600 g/l, the process comprises the steps of:
(a) dispersing a surfactant, and coating the surfactant with fine powder having a diameter from 0.1 to 500 microns, while wetting the surfactant coated with the fine powder with finely atomized liquid, in a mixer wherein conditions of the mixer include (i) from about 0.2 to about 5 seconds of mean residence time, (ii) from about 10 to about 30 m/s of tip speed, and (iii) from about 0.15 to about 5 kj/kg of energy condition, wherein first agglomerates are formed;
(b) thoroughly mixing the first agglomerates in a mixer wherein conditions of the mixer include (i) from about 0.5 to about 15 minutes of mean residence time and (ii) from about 0.15 to about 7 kj/kg of energy condition, wherein second agglomerates are formed; and
(c) granulating the second agglomerates in one or more fluidizing apparatus wherein conditions of each of the fluidizing apparatus include (i) from about 1 to about 10 minutes of mean residence time, (ii) from about 100 to about 300 mm of depth of unfluidized bed, (iii) not more than about 50 micron of droplet spray size, (iv) from about 175 to about 250 mm of spray height, (v) from about 0.2 to about 1.4 m/s of fluidizing velocity and (vi) from about 12 to about 100xc2x0 C. of bed temperature.
Also provided are the granular detergent compositions having a high density of at least about 600 g/l, produced by any one of the process embodiments described herein.
Accordingly, it is an object of the invention to provide a process for continuously producing a detergent composition which has flexibility with respect to density of the final products by controlling energy input, residence time condition, and tip speed condition in the mixers. It is also an object of the invention to provide a process which is more efficient, flexible and economical to facilitate large-scale production. These and other objects, features and attendant advantages of the present invention will become apparent to those skilled in the art from a reading of the following detailed description of the preferred embodiment and the appended claims.